They knew the Delano house far too well. It was where Christian Philip Oberender, then 14 years old, had murdered his mother in a shotgun ambush in the family rec room in 1995.

Now, 18 years later, Carver County Sheriff Jim Olson was sending his deputies back to the home where Oberender still lives. Just two days earlier, Olson had scanned the day's shift reports and froze when he tripped over Oberender's name. A scan of a Facebook page then showed firearms spread out like a child's trophies on a bed inside the home, along with notes about the Newtown, Conn., gunman who shot 20 children to death.

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Even more disturbing was the letter Oberender had written recently to his late mother, Mary: "I am so homicide,'' it said in broken sentences. "I think about killing all the time. The monster want out. He only been out one time and someone die.''

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Even though Oberender killed his mother with a firearm, even though he was committed to the state hospital in St. Peter as mentally ill and dangerous more than a decade ago, he was able to obtain a permit to purchase firearms last May. That piece of paper gave Oberender, now 32, the ability to walk into any licensed Minnesota retailer and buy any assault weapon or pistol on the rack.